Method for producing ammonia

Abstract

The invention relates to a method for producing ammonia (1), wherein a carbon-containing energy carrier flow (2) and an oxygen flow (3) from an oxygen-producing assembly (4) are fed to a synthesis gas reactor assembly (5) for obtaining a synthesis gas flow (6) with hydrogen and carbon oxides, wherein the synthesis gas flow (6) is fed to an adsorption device (7) for separating the synthesis gas flow (6) into a hydrogen flow (8), which comprises hydrogen, and a purge flow (9), and wherein the hydrogen flow (8) and a nitrogen flow (10) are fed to an ammonia reactor assembly (11) and converted into ammonia (1) there. The method is characterized in that the purge flow (9) is fed to a recovery device (12), which obtains a hydrogen-containing recovery flow (13) from the purge flow (9) and discharges a waste gas flow (14) therefrom, and that the hydrogen of the recovery flow (13) is at least partly fed to the ammonia reactor assembly (11) for conversion into ammonia (1). The invention also relates to a corresponding system for the production of ammonia (1).

We claim: 
     
       1. A method for producing ammonia, wherein a carbon-containing energy carrier flow and an oxygen flow from an oxygen-producing assembly are fed to a synthesis gas reactor assembly for obtaining a synthesis gas flow with hydrogen and carbon oxides, wherein the synthesis gas flow is fed to an adsorption device for separating the synthesis gas flow into a hydrogen flow, which comprises hydrogen, and a purge flow, and wherein the hydrogen flow and a nitrogen flow are fed to an ammonia reactor assembly and converted into ammonia there, wherein the purge flow is fed to a recovery device, which obtains a hydrogen-containing recovery flow from the purge flow and discharges a waste gas flow therefrom, and that the hydrogen of the recovery flow is at least partly fed to the ammonia reactor assembly for conversion into ammonia, wherein the waste gas flow comprises nitrogen the recovery device includes a membrane device for separating the recovery flow from the purge flow, so that the waste gas flow remains and that a part of the waste gas flow is used as a membrane rinsing flow for rinsing the recovery flow. 
     
     
       2. The method according to  claim 1 , wherein the adsorption device includes a plurality of containers with an absorbing agent and the adsorption device is configured for pressure swing adsorption and, alternately, the synthesis gas flow is conducted in at least one of the plurality of the containers in an adsorption phase at higher pressure for producing the hydrogen flow and the purge flow is let out from at least one other from the plurality of the containers in a rinsing phase at lower pressure, and wherein the adsorbing agent has a molecular sieve for separating hydrogen. 
     
     
       3. The method according to  claim 2 , wherein the adsorption device is configured for temperature swing adsorption and, alternately, the synthesis gas flow is conducted in at least one of the plurality of the containers in an adsorption phase at a lower temperature for obtaining the hydrogen flow and the purge flow is let out from at least one other of the plurality of the containers in a rinsing phase at a higher temperature. 
     
     
       4. The method according to  claim 1 , wherein the recovery flow is fed to the synthesis gas flow upstream of the adsorption device with respect to the process. 
     
     
       5. The method according to  claim 1 , wherein, for obtaining the purge flow, a nitrogen-containing rinsing flow, which consists substantially of nitrogen, is fed to the adsorption device. 
     
     
       6. The method according to  claim 1 , wherein the hydrogen flow has a molar fraction of at least 90% hydrogen. 
     
     
       7. The method according to  claim 5 , wherein the rinsing flow is obtained from an air separation unit for obtaining nitrogen and oxygen from ambient air and fed to the adsorption device, that the nitrogen flow is provided by the air separation unit. 
     
     
       8. The method according to  claim 1 , wherein the recovery device comprises a further adsorption device configured for separating the purge flow into the recovery flow and the waste gas flow, wherein the further adsorption device is configured for pressure swing adsorption and/or temperature swing adsorption. 
     
     
       9. The method according to  claim 1 , wherein the synthesis gas flow is fed to a carbon dioxide scrubbing unit for washing out at least a part of the carbon dioxide from the synthesis gas flow, wherein the carbon dioxide is washed out in the carbon dioxide scrubbing unit by a scrubbing medium comprising methanol. 
     
     
       10. The method according to  claim 9 , wherein the synthesis gas flow is fed to an absorption stage of the carbon dioxide scrubbing unit for absorbing the carbon dioxide into the scrubbing medium, and that the scrubbing medium is run through a loop in the absorption stage and in a regeneration stage of the carbon dioxide scrubbing unit for releasing carbon dioxide from the scrubbing medium. 
     
     
       11. The method according to  claim 10 , wherein the carbon dioxide from the scrubbing medium is released in the regeneration stage substantially by a pressure relief of the scrubbing medium, wherein the carbon dioxide is released from the scrubbing medium in the regeneration stage without heating. 
     
     
       12. The method according to  claim 1 , wherein the synthesis gas flow is fed upstream of the carbon dioxide scrubbing unit with respect to the process, to a shift device, that the synthesis gas flow fed to the shift device includes water, and that a water-gas shift reaction for converting at least a part of the carbon monoxide of the synthesis gas flow with the water into carbon dioxide and hydrogen takes place in the shift device. 
     
     
       13. The method according to  claim 1 , wherein the synthesis gas reactor assembly obtains the synthesis gas flow from the energy carrier flow by autothermic reforming with the oxygen flow, so that a catalytic partial oxidation provides the heat required for the endothermic reforming reactions, wherein the synthesis gas flow exits the synthesis gas reactor assembly with a discharge pressure of at least 70 bars.